Before you read any further, be aware that Mesmer was, personally, my favorite class, mechanics and lore-wise, in the original Guild Wars. And now, onwards to the pain.

I think Arenanet has, in the wake of all the player fervor and wild expectations on these forums and elsewhere, lost sight of what the Mesmer originally was.

The Mesmer was, originally, a master of illusions. As far as what Anet thinks, it still is. However, there are two main categories of illusions, and I cannot stress enough how significant the differences between the two are.

The first type of illusion is created through the manipulation of an opponent's mind. This means that the illusion is perceptible to only the target, and no one else. The advantage of this type of illusion is that it is not only limited to the visual, and indeed can be used to inflict intense agony in combat (if one's mind is convinced they are burning, for all intents and purposes besides physical damage they are burning). This is by and large the type of illusion that the Mesmer of the first Guild Wars worked with. Even if it was an illusion cast on multiple opponents, it would only ever affect those targets (as far as I know, there was no hex contagion) and would not affect anyone who was not targeted.

The second type of illusion is created through the manipulation of light/sound/other natural forces in order to make a convincing appearance. Unfortunately, this is mostly visual/aural, as it's rather difficult to give the illusion of any sort of feeling without actually directly affecting your opponent's minds. Also unfortunately, it looks like this is the direction in which the Guild Wars 2 Mesmer is going.

I'd like to go over a few points in the reveal trailer that have struck sore spots with me, since I've been afraid for a long time that this would happen. I feel like the Mesmer is drifting away from its roots in lore.

1st segment - Group stealth. This is a concept that works well with both concepts of an illusion caster. Mentally, the caster could tinker with the minds of the target(s) to make it appear as if there is nothing there, hiding whatever he/she wanted from sight, even as others are able to see whatever is being hidden from the target(s). Physically, the caster could bend light around a certain area, hiding all within it from sight. From the video, Anet appears to have chosen the latter. While mechanically it is easier to implement, it does not fit well lorewise with the mental-based Mesmer. Even if you were trying to explain it away as a mental illusion, why would the mesmer precast it on the ground instead of the illusion on the one chasing the party?

2nd segment - The crippling line. This stems from my concern over the Mesmer having ground-targetted effects that last for any length of time after being cast. While one could argue a Mesmer could lay mental tripwires all over the place, it would still take a force of will to actually enact the illusion that one had been crippled, an effort much more easily done by singly targeting an enemy, or even a group of them.

3rd segment - So mesmers can...teleport now. That's quite a stretch. Mesmers were never hailed as the masters of time and space, and having instantaneous movement like that, while flashy and nice, jangles awkwardly with the lore. I could accept it if she only made the monsters THINK she had moved, but after she is done she just casts another spell, shoulders her staff, and gazes off into the distance. Besides which, as third party observers who are (I am assuming) not affected by whatever spell she used to teleport, if it had been a mental illusion we would not have seen her teleport at all.

4th segment - Not much to say on this, since we can explain the illusions away as temporary and targeted towards the minds of the sylvari's enemy.

5th segment - Portals. See my previous point about teleportation. If it were purely an illusion aimed at the one target, third-party observers would not see the Mesmer teleport, nor would allies be able to use the portals. The "force lightning" I am going to withhold statement on until the spell is actually identified.

So there you have it, my lore/logic-wise concerns for the Mesmer. Sure it may LOOK flashy, but out of all the classes I believe it is the one with the least logical ground-targeted durational spells, and that is what's really bugging me.